1. Field of the Invention
The present invention relates to a noise-cancelling headphone with which one can enjoy music without being hindered by ambient noise by outputting a signal that cancels the ambient noise along with an audio signal and, more particularly, to a noise-cancelling headphone with which one can enjoy music with high sound quality without the change in sound quality and volume between when a noise-cancelling function is activated and when it is deactivated.
2. Description of the Related Art
A noise-cancelling headphone is desired, with which one can listen to music with high sound quality while cancelling ambient noise. In general, a noise-cancelling headphone has a microphone that picks up ambient noise to a headphone case etc., a cancel signal generation circuit that generates a signal (cancel signal) cancelling noise heard by the ears through the headphone case from the noise picked up by the microphone, and a mixer circuit that combines a music signal with a cancel signal and outputs the combined signal. When such a noise-cancelling headphone is used, if sounds informing of the surrounding circumstances (for example, sirens or horns) are cancelled by a cancel signal, there is a possibility that the safety of a headphone user is compromised. Consequently, a noise-cancelling headphone is known, which can be used comfortably while ensuring the safety of a user by selectively separating the “sounds informing of the surrounding circumstances” as “sounds interesting for the user” in consideration of the safety of a user and by generating no cancel signal against the “sounds interesting for the user” while generating a cancel signal against other sounds (ambient noises picked up by a sound pickup microphone) (for example, refer to patent document 1).
[Prior art document]
[Patent document 1] No. JP 2004-526375 W